I am sticking my neck out here for flaming, but here we go - reuse drives me mad! Or more to the point, the complete misuse of reuse.
A case in point is the hype surrounding SOA. Can any two people actually agree on what SOA is? No. But it seems that they can agree that its benefits are from reuse. Oh please!
Reuse is hard. A lot of time reuse doesn't offer any benefits, it doesn't make any business sense. Reuse for the sake of reuse leads to overly interdependent business applications and blurred boundaries of ownership and responsibility.
Seeing as I am a crap writer and don't want to bore you I'll point you to an article that gets across the point far better than I: Is SOA Another Fake Path to IT Agility?
Reuse? Reuse this - Thwack!!